Novel iniferter-based synthetic approach to hetero-telechelic precursors and multiblock copolymers composed of vinyl polymer blocks and condensation linkages

A novel synthetic approach, leading to the formation of hetero-telechelic precursors and multiblock copolymers composed of vinyl polymer [polystyrene or poly(N,N-dimethylacryl amide)] blocks and condensation linkages (ester or amide) or its polycondensate blocks, was developed using iniferters containing two different types of functional group (hydroxyl, carboxyl or amine) in their molecules via two different routes, each of which consisted of two-step reactions: photoiniferter living radical polymerization and subsequent polycondensation or vice versa. Both reactions proceeded at room temperature. The formation of multiblock copolymers was confirmed by 1H NMR and IR spectroscopic measurements and molecular weight measurements. Irrespective of the type of iniferter, the livingness of the iniferter polymerization step was verified by a linear relationship between the conversion and molecular weight under appropriate reaction conditions, indicating that the vinyl polymers' block lengths were well controlled. The decrease in molecular weight of copolymers subjected to mild alkaline hydrolysis indicated that these multiblock copolymers might be degraded in a living body. This study is preliminary, but synthetic strategy proposed here may enable various choices of macromolecular architecture. Once the optimized reaction condition is achieved, functional macromolecular architectures with sequentially ordered complexity including well-controlled block lengths and multiple condensation linkages are feasible.